1. Field
Embodiments relate to semiconductor devices and methods of fabricating the same, and more particularly, to semiconductor devices including MOS transistors including an optimized channel region and methods of fabricating the same.
2. Description of the Related Art
MOS transistors are widely used in the semiconductor devices as active devices such as switching devices. Specially, CMOS integrated circuits including NMOS transistors and PMOS transistors are widely used for improving standby current characteristic, which is one of electrical characteristic of semiconductor devices.
In general, CMOS circuits may include MOS transistors having a variety of channel widths. For example, the NMOS transistors and the PMOS transistors may have narrow channel widths that are equal to minimum feature size relevant to the resolution limit of photolithography process.
Meanwhile, to improve operating characteristics of a CMOS circuit, the NMOS and PMOS transistors may be improved in regard to current drivability. The current drivability can be improved by reducing threshold voltages of the MOS transistors. Recently, a technology to interpose a layer containing lanthanum between a gate electrode and a channel region is used in order to reduce the threshold voltages of the NMOS transistors. However, in case that a layer containing lanthanum is formed in NMOS transistors having narrow channel width, the threshold voltage of NMOS transistors having narrow channel width may be higher than that of NMOS transistors having relatively wide channel width. Thus, there are limitations to improving electric characteristics of the semiconductor device that includes NMOS transistors with narrow channel width.